Zesa Holdings will need to reduce average power output at anchor power station, Kariba South by 5.3 percent to 445 megawatt after the Zambezi River Authority (ZRA) cut the water allocation for electricity generation by 5.3 percent from 38 billion cubic metres to 36 billion cubic metres.
Kariba South can generate up to 1 080MW but there is never enough water for Zesa to run the station at this level for more than a few hours a day to cope with peak demand and then run it at lower levels for the rest of the day.
Kariba South Extension gave Zesa the capacity to cope with peak demand but then the utility had to cut right back late at night to keep within its water ration, even in good rainfall years.
ZRA had warned that if water allocation at Kariba was not reduced and power generation continued at levels above 1 000 megawatts, all power generators at Kariba would be forced to shut down by November 2019.
Zesa and its fellow Zambian State-owned power utility, ZESCO, share the water in the Kariba Dam equally for electricity generation on the northern and southern sides of Kariba Dam wall. As such, the directive also affects Zambia, which is also heavily dependant on Kariba for power.
ZRA said the downward adjustment in water allocation for power generation at Kariba means Zimbabwe and Zambia should produce power generation at Kariba at a maximum combined level of 890MW; or 445MW apiece.
This state of affairs will subsist until, at the earliest, the end of this year when there will be more data on expected inflows. Kariba is currently Zimbabwe's most reliable power station at a time Hwange Thermal Power Station, which has rated capacity of 920MW (but producing to a maximum possible level of 700MW due to old age), can only manage 450MW at most.
Zesa said yesterday it will abide by the ZRA directive, but warned that the development would inevitably force it to reduce power generation at Kariba, ZRA said it had reduced water allocation from 38 billion to 36 billion cubic metres to ensure continued availability of water for power generation at Kariba following adverse hydrological situation in Kariba Dam's catchment area.
Kariba Dam has a prescribed water level called "live water", which ZRA maintains; this is the water above the entry tunnels to the turbines that drive the generators. ZRA administers all affairs relating to the Zambezi River, which feeds Kariba Dam, on behalf of riparian States, Zimbabwe and Zambia hence the latest directive.
"Please note that the hydrological simulations carried out by the authority in February 2019 have indicated that if the water allocation is not adjusted downwards by 2 BCM (billion cubic meters) by March 1, 2019, the continued below normal rainfall coupled with a continuation of generation levels at Kariba above 1 000MW will result in a shutdown of power plants at Kariba by November 2019," ZRA.
ZESA spokesperson Fullard Gwasira yesterday said the power utility will comply with the directive by ZRA, which it consented to, was necessitated by poor rains experienced last season in the catchment area.
"The reduction has an impact on national local generation as Kariba South is the anchor station in the country and the reduction will therefore mean that there is a demand and supply mismatch, which we have to manage through load shifting or curtailment to ensure stability of the grid," he said.
Gwasira also said plans were underway to improve efficiency and reliability of Hwange Power Station, which should ordinarily be the anchor power station, but is being bogged down by old age and foreign currency shortage needed to procure spares, Munyati and Bulawayo power stations.
He said that consumers should play their part and conserve energy, by switching off all unnecessary lights and electronic gadgets and take advantage of off peak periods, to minimise the extent and duration of load shedding. Zimbabwe-which requires about 1 600MW at peak periods of demand, against local generation potential of only 1 400MW (with Kariba at full throttle)-last experienced load shedding more than four years ago.
Zimbabwe has been importing from Mozambique and South Africa to bridge the gap between demand and supply. However, power imports from South Africa's Eskom cannot be guaranteed, as the utility is also facing a fair share of own challenges.
Technical issues at Eskom have in recent months affected generation, resulting in demand-supply mismatches in Africa's biggest economy. The Zimbabwe state power utility also has outstanding dues to Eskom for supplies in the past, making imports from that country hard to depend on.
Regardless, Zimbabwe's foreign currency situation has deteriorated; making sustaining imports even more difficult at a time the country's is also battling to mobilise adequate forex for importation of fuel.